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By Meyer C. F

The increasing use of continuous miners in the extraction of high coal seams has amplified the need for enhanced ventilation systems in the headings. Owing to larger face dimensions and higher production rates, more ventilating air is required to effectively dilute liberated methane to acceptable concentrations. However, the increased air quantities raise and entrain greater amounts of dust, to which the operator is subjected. Various methods (eg sprayfans, on-board scrubbers and jet fans) are used in various configurations and combinations to ventilate the headings. These arrangements generally result in a complex air flow pattern, which complicates achieving an optimum balance between diluting methane and minimising dust capture. In order to cost effectively investigate and propose solutions to this problem for the South African coal mining industry, the Division of Mining Technology has embarked on an extensive work program to evaluate various ventilation methods presently in use. Four currently generic ventilation patterns in various heading scenarios have been simulated using the Computational Fluid Dynamics (CFD) computer program. Evaluating these outputs against a predetermined set of criteria allows the best system for a particular situation to be chosen. The program also facilitates fine-tuning of an adopted system without incurring the cost and inconvenience of doing such tests in situ. This process not only provides solutions at significantly reduced costs, but also yields deeper insights into the factors affecting heading ventilation than hitherto possible.

Jan 1, 1995

By Shuguang L, Jing S

Computer controlled truck dispatching systems is a newly-developed technical system in surface mines with shovel-truck technology. The real time dispatching criteria, as the core of optimal truck dispatching software, are analysed and a new criterion, complex dispatching criterion, is put forward. Dispatching criteria previously proposed include: 1. `Earliest Loading' (EL) - to assign a truck to the shovel at which the truck can be loaded earliest. 2. `Max Truck' (MT) - to assign a truck to the shovel at which the truck will have the shortest waiting time. 3. `Max Shovel' (MS) - to assign a truck to the shovel which has been waiting for the longest time. 4. `Minimum Saturation Degree' (MSD) - to assign a truck to the shovel at the branch where the truck flow saturation degree is minimum. 5. `Minimum Saturation Degree with Truck Cycle time consideration' (MSDTC) - as the MSD principle, with the truck travel cycle also considered. 6. `Fixed Dispatching' (FIX) - to assign trucks to fixed shovels. A system simulation model has been set up for truck dispatching system analysis. A few surface coal mines have been selected for case studies. Equipment waiting times and shift production of the system are obtained as the main outputs of the model. Simulation results show that each dispatching criterion has its own applicable range, no one can absolutely dominate the others. For example, when under-trucked, EL and MT criterion can obtain higher production than the MS criterion; when over-trucked, it is vice versa; while for MSD criteria, better results can be obtained no matter how the truck numbers fluctuate. From the view point of shovel output balance, large fluctuations occur for EL and MT criteria, while a good balance can be obtained for other criteria. In the light of dynamic change of mining system conditions, a single dispatching criterion is not necessarily reasonable. A complex dispatching criterion has been put forward to seek the complex optimum effect. Taking the advantage of each dispatching criteria, the dispatching result of a complex dispatching criterion dominates over individual dispatching criterion and a comprehensive optimum effect can be reached.

Jan 1, 1995

By Battino S

ABSTRACT' The high gas emissions associated with coal extraction at some-Australian collieries have provided a need to investigate the methods used to predict these gas levels and the vent- ilation requirements for gas dilution. It is generally accepted that the introduction of longwall extraction in particular is associated with complex ventilation planning problems. These problems are made much more severe when the colliery introducing longwalls is already facing high gas emissions even during the development stages. A forecast of likely gas emissions during the longwall mining process indicated possible ventilation problems in maintaining the necessary ventilation levels to satisfy the statutory gas limitations for various production rates. Although there are sound principles used in world recognised methods of gas emission prediction a new approach developed from the findings of the Barbara Experimental Mine in Poland appears most suitable for Australian conditions. This has been applied to an Australian colliery preparing for longwall mining using statistical methods for air

Jan 1, 1983

The stratigraphic sequence west of Mount Isa contains the Judenan Beds, Eastern Creek Volcanics, and May Downs gneiss. It is an incomplete sequence as major north-south faults divide the area into four separatezones containing portions of these different units. The first three zones, which occur directly to the west of the Mount Isa Fault, consist of quartzites and quartz-mica schists which are uncorrelatable between zones but have been grouped together as the Judenan Beds. The most western zone contains an incomplete section of Eastern Creek Volcanics which rests conformably on a unit believed to be equivalent to the Mount Guide Quartzite; this is again underlain by the May Downs gneiss. A detailed description of the rock types is presented, but only a broad stratigraphic correlation is possible with the very much thicker sequence to the east of Mount Isa.The age of sedimentation is believed to be Lower Proterozoic and it may not occur in the type of geosynclinal basin envisaged by previous authors.This sequence is intruded by many small basic intrusions and also the Sybella Granite with its associated microgranite and pegmatites. The Sybella Granite consists of both a massive and a foliated phase; the latteris generally restricted to the margin of the main granite mass.Four regional metamorphic zones have been identified on the basis of their pelitic mineral assemblages; these are a chlorite, biotite, biotite-cordierite, and a sillimanite zone; separating each are prominent north-south faults.This metamorphism is a regional metamorphism which accompanies the first generation folding of the area and is not associated with the emplacement of the Sybella Granite. A very localized retrogressive metamorphism is also found in some areas of second generation folding.

Jan 1, 1972

At the Nikkel og Olivin nickel mine near Narvik, Norway, Outokumpu has been the operator since 1993. The mine was opened in 1989 and in 1992 Outokumpu commenced operations to secure concentrate deliveries to Harjavalta's nickel smelter in Finland. Annual production is about 740 000 tonnes of nickel ore grading 0.5 per cent Ni, about 25 000 tonnes of nickel concentrate and about 2800 tonnes of nickel metal. All production comes from underground operations which makes Nikkel og Olivin AS perhaps the lowest grade underground nickel mine in the world today. Production is currently from one of two orebodies, which is known as the Western orebody. The Eastern orebody was worked out by 1995. During Outokumpu's operational period the Western orebody has been delineated and taken to production. The underground exploration and definition drilling involved about 15 000 in of diamond drilling, which was carried out during a nine-month period. Following this a feasibility study was undertaken and production commenced. Improvements were made to the mining methods. Previously the mine utilised open pit equipment underground and this resulted in an enormous amount of additional tunnelling. Grade control and ore delineation were previously based on sparse diamond drilling and all geological information was processed manually. The improvements included the use of underground sludge drilling to increase the amount of geological information, the of a new computer system for grade control and mine planning, new automated underground longhole drilling equipment and the of underground mining equipment which reduced the size of the drives. These changes produced a marked increase in the efficiency of the underground Mine.

Jan 1, 1996

By Milawarma E, Cusack C

The Sapan Dalam coal deposit of Indonesia consists of ten steeply dipping seams with thicknesses varying between 0.1 and 3.5 m and split by shale, clay, silt and sandstone. The area contains four faults dipping about 75¦ with four to 85 m vertical displacements. The complex nature of the deposit coupled with limited 27 exploration drillholes at an average spacing of 200 m made it difficult to create a realistic geological model. A three-dimensional gridded seam model gave a fair representation of the deposit. Attempt to create an optimum pit using the WHITTLE 3D pit optimiser proved unsuccessful since the pit optimiser is restricted to standard regular or fixed blocks. The gridded seam model was converted to a fixed block model prior to the optimum pit design. Smoothing and pit base controlling were also introduced to obtain a smoother pit. A mining scenario produced 3.6 million tonnes of coal, 28.4 million bcm of waste and US$18.1 million revenue.

Jan 1, 1995

By Gordon A. R

The effect of various types of solid carbonaceOlls reductants on the rate of fuming of zinc from lead blast furnace slag was investigated at I250°C.The results of the laboratory experiments indicated that the rate of removal of zinc from slag depended primarily on the volatile matter contents of the reduclants. The effects of fixed carbon, moisture and ash contents were less significant.

Jan 1, 1992

By Best R. J, Poulos H. G

The method for design of primary roof support for the large todoidal cavern constructed to house the Sydney Opera House parking station is presented. The cavern was constructed with 5 m of rock cover beneath Sydney's Royal Botanic Gardens. Design of rock reinfonnent using a combination of fully grouted rock dowels and Macalloy bars was based on control of horizontal shear movement along bedding features in the roof. A combination of linear arch type analyses and non-linear jointed finite element analyses were used in the design study together with an analysis of the shear resistance offered by fully grouted bolts under shear deformation.

Jan 1, 1993

By Savidis G

The characteristics of 'Z' (Back-over run) and 'R' (Reverse) ventilation systems are dis- cussed in relation to their suitability for longwall mining. Experience in European mines has been described as a basis for comparison with Australian conditions. In assessing the merits of each ventilat- ion system, such factors as longwall layout (pillar design, number of headings and gateroad stability), the need for gas drainage and bleed- er systems, as well as the influence of seam dip have been considered relevant. The R system is generally applicable for single and two heading development in seams where gas emission is a less serious problem. In contrast, the lower extraction to development ratio of the Z system (which arises from using three or more heading layouts) is considered more favourable where high gas emission occurs. The Z system provides greater flexibility with respect to the provision of refreshing air at the tailgate end, access of men and materials, installation and retrieval of gas drainage systems and the ability to interchange main- gate and tailgate roadways in cases where roof strata loads are difficult to control, or where cpam in hac an influrnra

Jan 1, 1983

By Murphy MW, Klaric SD

The history, operation and design of the Secor continuous rod production process is described. The effective operation of the plant is influenced by accurate monitoring and control of molten metal properties, mould release application, coolant application and composition and correct setting of all operating parameters. The continuity of operations, which is an essential feature of this type of plant, is also greatly influenced by the service life of wear parts in the operation. This paper deals with three principal wear parts which come into direct contact with copper during operation, these are:

Jan 1, 1985

By Andrews JRG

Chrysotile asbestos is a valuable resource. Used as a reinforcement in asbestos cement, products are obtained which are cheap, are not attacked by vermin, do not rot or support growth of fungi and are unaffected by water or humid conditions. Such products are of great value in the developing countries where inexpensive and durable building materials and pressure pipe are very important to development, housing and water supplies. Concern over the adverse effects of inhaling asbestos has led to the introduction of increasingly stringent controls world wide on the quantities of airborne asbestos per- missible in the occupational situation. Wet processing has the potential for virtually eliminating the environmental concerns with asbestos dust both in fibre production and in the materials handling section of the manufac- ture of asbestos cement products. In addition, high efficiencies associated with wet process- ing mean that better yields are obtained and that the tailings which are dumped have a lower residual asbestos content. Since early 1977, ICI Australia and Woodsreef Mines have been engaged in a programme of research to develop and evaluate a wet mill- ingprocess to produce, from ore and existing tailings, high grade fibre suitable for use in asbestos cement products. The process has been developed through microscopic studies, labora- tory bench scale experiments, work in a small scale semi-continuous plant and product evalua- tion on experimental size Hatschek asbestos cement machines. A prototype mill with a normal feed rate of 1z tonnes per hour and capable of producing pipe grade asbestos from Woodsreef ore has been constructed and was operational from January, 1982 to July, 1983. A range of asbestos cement products have been made successfully on full scale Hatschek machines using fibre from ore and tailings milled in the prototype mill. Economic evaluations indicate that a wet process mill would be cheaper to build, operate and maintain than an equivalent dry process plant. A commercial plant has been designed 1. Manager New Process Development, Woodsreef Mines Limited, Barraba, Australia. 2. Senior Lecturer, Department of Chemical Engineering, Monash University, Vic, Australia. formerly Senior Research Officer, Research Department, ICI Australia Limited

Jan 1, 1986

By Kerr I. D, Kennedy M

Flash X-radiographs were obtained of commercial electric No 6 and No 8* strength aluminium tube detonators in small-diameter cartridges of emulsion explosive at various times after fusehead operation. The trigger system for the radiography was based on the detection of light following fusehead firing via optical fibres inserted into the fusehead cavity during detonator assembly. These experiments were simulated using a finite element hydrocode with realistic treatment of the non-ideal reaction kinetics. Excellent agreement was demonstrated for the shape and position of the shock waves. In both cases, initiation of the emulsion was predominantly forward from the detonator. For the No 8* strength detonator, this initiation resulted from the shockwave delivered through the sides of the detonator, while for the No 6 strength detonator, initiation was the result of a complex interaction between shockwaves originating both from the sides and from the endcap. In the reverse direction (towards the crimped end of the detonators), initiation was only weakly dependent on detonator strength, being controlled mainly by the competing processes of rarefaction from the cartridge boundaries and comer turning of the detonation wave from the forward initiation. The consequences for field performance of small-diameter emulsions will be discussed.

Jan 1, 1990

Optimum selection of explosives by means of monitoring explosive performance can lead to increased profitability through the control of fragmentation, a reduction in hangingwall and footwall damage and overall drill and blast costs. Studies conducted at the Mount Lyell Mining and Railway Company underground copper mine evaluated in situ the performance of four explosive types. Measurements included monitoring the levels of induced shock energy and the attenuation thereof with distance. The velocity of detonation (VOD) of these explosives was also measured using in-hole techniques. Assessment of these results, together with a knowledge of the rock mass strength, facilitated the selection of an explosive that was best suited to the given rock mass conditions.

Jan 1, 1995

By Firmin K

The Mt. Tom Price orebody of Hamersley Iron Pty. Limited consists of a folded hematite - shale sequence capped by a layer of goethite. Consequently, variations in iron content occur within the orebody, and as the overall grade is below that required to make specification products, selective mining must be carried out. A necessary preliminary to quality control'of products based on selective mining is the production of advance data, on the tonnages and grades of material to be expected in future mining areas. Bench plans showing zones of different grades and types of material anticipated are prepared from structural geological information. The grades of materials on a bench are essentially governed by the positions and attitudes of the shale bands. Quality control is exercised by blending different grades and types of material in primary crusher feed. Iron grade is the prime grade consideration although sometimes the level of phosphorus content must be considered. Pre-production grades Are determined from assay of samples taken from blasthole cuttings.

Jan 1, 1980

By Monette J. C, Nulty J. H

High temperatures and pressures are required to obtain acceptable stripping rates. Higher chemically induced stripping rates could reduce the need for higher temperatures which lead to cyanide losses. The higher rates could lead to lower carbon inventories and higher gold production. This paper reports laboratory and continuous test unit data which strongly suggest that the preceding can be achieved. New stripping agents demonstrate efficient stripping under conditions of cyanide depletion such as after carbon acid washing. Stripping times for gold and silver can be reduced by at least half compared to caustic cyanide through the use of these novel substances.

Jan 1, 1991

By Torres F, Cerda I, Gimenez P, Gonzalez G, Castelli L

Slurry density measurement, specially in cyclone feed streams, is fundamental to grinding circuit control. With the purpose of increasing the availability of such a measurement, the design of a soft-sensor in an actual grinding plant is addressed in this paper. The system is designed to substitute the momentary unavailability of the real density sensor, either because it has failed or because it has been removed for any other reason. The ARMAX model structure is determined using the stepwise regression method. Starting with a list of the candidate variables, the method selects, one by one, and in a systematic manner the variables which best model the measurement to be replaced, choosing them from the set of presumably correlated candidate variables. In this paper not only the single measurements are included in the list of candidates, but also combinations of such measurements having physical significance. A phenomenological model has been built with the purpose of determining these combinations. It turned out that in most of the cases the components of combined measurements having physical significance were selected by the stepwise regression method, instead of the single measurements. Actual grinding plant data is used to determine the model structure, to estimate the model parameters and to test the predictive capability of the developed soft-sensors. Good results are shown to be obtained during periods of up to 30 hours of the density soft-sensor operation.

Jan 1, 1995

Every text book for blasting in Japan says that Hauser's law can be applied for practice. But recently it came true that there was no historical record about him and no actual datum of his own or other's to testify. According to his theory, the funnel ratio N = r/W in crater test is inversely proportional to the rock strength and proportional to the explosive amount: where r is the radius of crater and W is the burden. But experiment showed the opposite result, and revealed new information. Two kinds of experiment, crater test and boulder blasting of mortar, were carried out to investigate the effects of rock properties on blasting. The material used for test 1 and test 2 was a mortar block (60cm)3 cube, 4 vertical faces of which were used for crater test. The results from Test 1 and test 2 were summarized as follows. The funnel ratio ranges between 2.5 to 4.5 in proportion to rock strength and burden. The standard ratio of 1, reported by Hauser, was not observed in any instances. It was also noted that the funnel ratio is independent of the explosive amount. The material used for boulder blasting, test 3, was a mortar block (40cm)3 cube, in the middle of which was located a vertical borehole for the explosive charge. The results of test 3 were as follows. The necessary explosive amount for boulder blasting is in inverse proportion to the mortar strength. Fragmentation and throw are proportional to the mortar strength.

Jan 1, 1990

The need for the hydraulic transportation of coal in the New South Wales coal industry, both from the coal face to the surface and from the coal mine to the consumer or the port for export, is explained. Details of research projects currently in progress and involving the hydraulic transportation of New South Wales coals are given together with information on the hydraulic transportation of coal in the United States of America. The potential of hydraulic transportation as a viable alternative to the proposed expansion and upgrading of the New South Wales railway system to meet the projected New South Wales coal production to the year 2000 is described.

Jan 1, 1980

The exploration and mining risks are investigated and compared to the risks of smelting, secondary processing and other normal industrial activities. This study concentrates on the risk before, or at the investment decision. Internal and external risks are distinguished. Internal risks are the risks inherent in every engineering design and common to all projects. The main external risks are the financial risk, changes in prices, location problems and geological factors. Financial risks concern every capital-intensive and export-oriented project and cannot be considered as typical mining risks. Changes in prices, i.e. the market risk, concern every industry using raw materials, but the market risk is especially accentuated in the mining industry. Problems of location and infrastructure are normally more significant in mining than in other projects, and geological risks are unique to mining. All these risks associated with mining projects combine to form a risk at least twice as high as that for other normal industrial activities. Within the range of profitability of mines, which on average is the same as in the manufacturing industry, only a few highly profitable mines exist. These few mines are the sole reward for the high risks taken.

Jan 1, 1986

The recent installation of top gas temperature probes in blast furnaces at Australian Iron & Steel Pty. Ltd. - Port Kembla, has provided the means for studying radial gas flow distribution in blast furnace shafts. This paper describes the top gas temperature probes and outlines their development and results of initial studies aimed at obtaining a suitable relationships between temperature profiles and furnace parameters. The effects of various combinations of burden materials have been outlined by the results reported. The use of probes has also helped to clarify the effect of casting cycles on furnace operation leading to increased emphasis on the reduction of the interval between gun-up and drill-out. Areas for future studies are also broadly Outlined.

Jan 1, 1975